1. Field of the Invention
The present invention relates to a reception apparatus suited for a base station, a terminal station or the like of a radio data transmission system for estimating the state of a transmission channel using a known signal.
2. Related Art Statement
At present, demand for cellular phones, radio LANs and the like rises and a radio communication system plays a very significant role.
The radio data transmission system is quite advantageous over a wire data transmission system in portability, easiness of installation, cost and the like. However, since the radio data transmission system transmits data through radio transmission, the state of a transmission channel has a great change even while communication is being held and the system is influenced by a multiple reflected radio wave propagation (multi-path). Due to this, the communication quality of the system sometimes deteriorates greatly.
Considering this, a method of transmitting a known signal (preamble) prior to or posterior to a signal for transmitting information is often adopted. According to this method, a reception side measures a transmission channel response from a reception preamble and compensates for a distortion given to a signal on the transmission channel using an estimated transmission channel response based on a measurement result.
As can be seen, a technique for transmitting a preamble to estimate a transmission channel and for allowing a reception side to estimate the state of the transmission channel based on a reception result, is an effective method for the reception side to eliminate an influence on the signal on the transmission channel.
This method, however, has disadvantages in that a reception preamble is unavoidably influenced by the noise of a receiver and the state of a transmission channel cannot accurately grasped.